This application is based on application No. Hei 11-275381 filed in the Japanese Industrial Property Office on Sep. 28, 2000, the content of which is incorporated hereinto by reference.
(a) Field of the Invention
The present invention relates to a negative active material for a rechargeable lithium battery, an electrode for a rechargeable lithium battery, a rechargeable lithium battery and a method of preparing the negative active material for a rechargeable lithium battery and, more particularly, to a negative active material for a rechargeable lithium battery including a particle-agglomerated product.
(b) Description of the Related Art
The development of miniaturized, light and high performance electronics has provoked the need for a rechargeable battery having a high capacity.
It has been known that graphite with a theoretical capacity of 372 mAh/g exhibits a higher capacity than other negative active materials. In order to increase the capacity of rechargeable lithium batteries, studies on a new negative active material with a higher capacity than graphite have been undertaken. The studies have been done to develop either a new material which is different from graphite, or a mixed material including a graphite core.
Tin compounds have conventionally been considered as negative active materials to replace graphite. It is known that tin in the tin compounds makes an alloy with lithium that exhibits a higher discharge capacity than graphite.
The tin compounds, however, have lower initial charge and discharge efficiency, bad discharge curve flatness and inferior charge and discharge cycle characteristics, when compared with graphite. These drawbacks make it difficult to use tin compounds for negative active material in a rechargeable lithium battery, but attempts to use tin compounds have continued because in they have the unneglectable advantages of greater charge and discharge capacity over graphite. It is expected that a fantastic negative active material may be obtained when tin compounds are mixed with graphite.
Recently, a negative active material with a mix of graphite and tin compound has been suggested. The negative active material can be densely coated on an electrode because graphite has a flake configuration, but the resulting electrode exhibits low wettability to electrolyte and thus the charge and discharge reaction cannot be readily produced because of graphite.
It is an object of the present invention to provide a negative active material for a rechargeable lithium battery having high charge and discharging capacity, high charge and discharge efficiency, good discharge curve flatness, good charge and discharge cycle characteristics and high packing density.
It is another object to provide a method of preparing the negative active material for a rechargeable lithium battery.
It is still another object to provide an electrode using the negative active material.
It is still another object to provide a rechargeable lithium battery using the negative active material.
These and other objects may be achieved by a negative active material for a rechargeable lithium battery including a particle-agglomerated product. The particle-agglomerated product includes a carbonaceous material into or from which lithium is intercalated or deintercalated, and an amorphous metal compound that is able to become an alloy with lithium.
The present invention provides a negative electrode for a rechargeable lithium battery including the negative active material and a rechargeable lithium battery including the negative active material.
The present invention also provides a method of preparing a negative active material for a rechargeable lithium battery. In this method, a fatty acid metal salt is added and agglomerated with a carbonaceous material to produce an agglomerated precursor, and the agglomerated precursor is then heat-treated to convert the fatty acid metal salt into the amorphous metal compound and to produce a particle-agglomerated product.